A visibly emotional Donald Tusk told reporters that he and the European Union's remaining 27 member states already missed the UK.

During a press conference shortly after receiving the letter from the UK's permanent representative to the EU, Sir Tim Barrow, confirming Britain's decision to leave the EU, the president of the European Council said: "What can I add to this? We already miss you. Thank you and goodbye."

He opened his brief statement by saying: "There is no reason to pretend that this is a happy day, neither in Brussels, nor in London. After all, most Europeans, including almost half the British voters, wish that we would stay together, not drift apart. As for me, I will not pretend that I am happy today."

"There is nothing to win in this process, and I am talking about both sides," Tusk added. "In essence, this is about damage control."

During his remarks, Tusk told reporters Brexit had made the remaining member states more united, and that they would remain so in the negotiations ahead. He said the EU had a strong mandate to protect the interests of the 27 member states.

Tusk also confirmed that the first step of the process will be the adoption of guidelines for the negotiations when the 27 member states meet on 29 April.

Finally, Tusk said EU law would continue to apply in the UK until it had fully withdrawn.

In a written statement, the European Council noted that the guidelines would set out the overall positions and principles on the basis of which the the 27, represented by the European Commission, will negotiate with the UK.

The statement said the bloc will act “as one”, and its first priority will be to “to minimise the uncertainty caused by the decision of the United Kingdom for our citizens, businesses and Member States. Therefore, we will start by focusing on all key arrangements for an orderly withdrawal."

By the end of the week, Tusk is expected to circulate a draft of the negotiating guidelines with the 27 capitals. These are said to limit the scope of the upcoming talks to agreeing the terms of the departure ahead of any talk about a future trade relationship with the UK.

The EU’s chief negotiator Michel Barnier, backed by the 27 member states, has made clear the two sides must settle the principles of withdrawal, including the rights of EU nationals living in the UK and the Britain’s existing financial and EU budget commitments, before moving on to discuss the terms of the future EU-UK trade relationship.

Negotiations proper are not expected to begin before the end of May.

Alberto Nardelli is Europe editor for BuzzFeed News and is based in London.